EBME & Clinical Engineering Articles

Killing Super-bugs with Ultra-violet light

Creating a healthy pathogen free environment is a difficult business. It is vital to control airborne infection, whatever the environment now and continuously into the future.

UVC air sterilisation is a proven and tested solution against airborne infection. Using existing technology, many Hospitals globally are already successfully reducing air-borne infection within medical, workplace and educational facilities.

From hospitals and laboratories to offices, leisure, schools and colleges, they are achieving a reduction of 99.9% for each target organism using UV air purifiers.

Airborne infection-a silent threat.

Throughout the world of healthcare the dangers to patients and EBME / medical staff of airborne organisms present a major challenge to infection-control professionals. There are many airborne pathogens that exist within medical equipment, such as the ventilators, nebulisers, suction devices etc.

When the devices are switched on for test, they can release a variety of unhealthy bugs into the environment of the EBME workshop. These bugs are also present in the patient environment and impacting not only on patients but also on clinical staff.

In the UK alone the cost of hospital-acquired infection is estimated at £1 billion per year. A recent report from the US Centre for disease control stated that "hospital-acquired infection is a global problem and is the fourth greatest cause of mortality amongst Americans". Attempts to contain this problem have created a situation where, of the top six bacteria found within hospitals, each is resistant to at least one drug. This lack of the effectiveness of existing antibiotics is forcing a treadmill of new, more expensive drugs, and yet further resistances. Infection is spread in many ways, however, the two most commonly encountered methods contact and inhalation. Historically, regular surface cleaning and hand-washing was the accepted way to combat these infection risks. Although these actions are vitally important, little is currently done to reduce the risks from inhalation of airborne micro-organisms.

UV technology - a solution to the airborne infection.

Ultraviolet light occurs naturally in sunlight and may be divided by wavelength into three bands, A,B,& C. Of these UVC is the shortest and most powerful. At the specific wavelength of 253.7 nm. It is proven to be deadly to viruses, bacteria and moulds. A UVC air purifier exposes air passing through the units radiation chamber to an intense amount of UV energy, in such a way that it acts as a highly effective germicidal sterilant. The short propagation distance of UVC has been employed to avoid leakage of any potential actinic rays, which may affect the user.

The technology:

Four 25Watt UVC tubes that have been engineered into a reflected array to produce an intense energy field capable of eradicating the most resistant micro-organisms. Energy output equals 23.868 µW Sec/cm2

Slow airspeed increases exposure time to the UVC. But mathematically modelled chamber design ensures the air is maintained in close proximity to the radiation source. This provides maximum killing power for the toughest bacteria, germs, spores and moulds. These devices do not require a large space, are low energy, and are relatively quiet. They can easily and quickly be installed to any solid surface and require only a standard power socket. It is intended that the unit is operated 24/7 days, providing continual air sterilisation without the need for operator supervision. Any EBME technician could easily maintain these unit. In support of the usual hand washing and surface cleaning regimes, UVC now provides a further dimension to infection-control.

Microbiology.

UVC units have been exhaustively tested in the field and the laboratory. Exceptional performance against an array of pathogenic micro-organisms has been achieved.

Laboratory tests:

A range of trials performed by Micro research laboratories - an independent UKAS accredited laboratory - employed a number of different test protocols to measure UVC efficacy. Results against the three strains of staphylococcus aureus (NCTC. 119 39, and in 1940, and 119 62), proved the effectiveness of the UVC unit under test, removing 99.999% of these virulent strains from the test environment. Tests against organisms that are both airborne and normally static proved equally effective. Efficacy was established beyond doubt by demonstrating seven log cycles of kill over an eight-hour period, these devices prove very effective across a wide range of genre, including gram-positive, gram-negative bacteria, yeasts and moulds.

Clinical trials.

Two UVC units were positioned within the high dependency unit of a leading hospital operated by BMI, the UK's largest independent healthcare provider.

Air sampling was carried out using Casella air sampling equipment. Measurements were taken several times each day over a recommended period of time. The results were compared with and without the presence of the UVC unit. An array of organisms commensurate with a typical clinical environment were recovered from the atmosphere during the control period. Crucially, these organisms were significantly reduced or eliminated during the control period whilst the 2 UVC units were in operation. A reduction of 99.999% was achieved for each target organism. This clearly demonstrates a significant contribution to atmospheric treatment in a clinical environment. Overall, the statistically significant reduction in the airborne levels of gram-positive and gram-negative organisms could be attributed to the in-situ use of the UVC unit.

Air Dynamics.

A key measure of the effectiveness of an air sterilisation unit is its ability to fully circulate all the air in the room, ensuring a uniform and continuous distribution.

To evaluate the 2 UVC units performance, QinetiQ PLC-Europe's largest science and technology Organisation-used advanced computer computational fluid dynamics to determine the ability of a single UVC unit to process the air in a single standard test room. The results demonstrated that the UVC units operated by creating a temperature gradient that in turn caused a thermally driven airflow. This ensured that the air throughout the whole room was fully processed. UVC air purification reduced the amount of contamination by 50% after 12 hours and 47 minutes. The research, undertaken in a room four times the size recommended of a single UVC unit, shows the units proven ability to circulate the air and eliminate the harmful microbes. These independent research reports demonstrate the its ability to eradicate organisms, deliver air circulation and as such provide total confidence in the ability of UVC to engineer air sterility.